I'm actually half on the officer's side here
The mistake (probably intentional, therefore only half on the officer's side) was not informing the chap at the start. Recording interactions with people who are known to make complaints about your particular organization or group is only self defence.
One segment beggars belief however: "it's for the court to decide whether it's being used for surveillance, not the officer"
What the actual feck? Are the court claiming they know the officer's mind better then the officer himself or.... am I misreading it?